Synopsis The aircraft, a Pilatus PC-12, serial number 151, was on a scheduled domestic flight from St. John's, Newfoundland, to Goose Bay, Labrador, with the pilot, a company observer, and eight passengers on board. Twenty-three minutes into the flight, the aircraft turned back towards St. John's because of a low oil pressure indication. Eight minutes later, the engine(Pratt Whitney PT6A-67B) had to be shut down because of a severe vibration. The pilot then turned towards Clarenville Airport, but was unable to reach the airfield. The aircraft was destroyed during the forced landing in a bog one and a half miles from the Clarenville Airport. The pilot, the company observer, and one passenger sustained serious injuries. The Board determined that the pilot did not follow the prescribed emergency procedure for low oil pressure, and the engine failed before he could land safely. The pilot's decision making was influenced by his belief that the low oil pressure indications were not valid. The engine failed as a result of an interruption of oil flow to the first-stage planet gear assembly; the cause of the oil flow interruption could not be determined. Ce rapport est galement disponible en franais. 1.0 Factual Information 1.1 History of the Flight The aircraft, operating as Kelner Airways Flight 151, departed St. John's, Newfoundland, for Goose Bay, Labrador, on an instrument flight rules (IFR)(1) flight at 1655 Newfoundland daylight saving time (NDT)(2) with the pilot, an observer, and eight passengers on board. As the aircraft approached the planned cruise altitude of 22 000 feet (FL220), the pilot noted an unusually low indication on the engine oil pressure gauge and, just prior to levelling off at FL220, the low oil pressure caution annunciator light activated. Upon levelling off at FL220, approximately 39 nautical miles (nm) from St. John's Airport, the low oil pressure warning annunciator light activated. The pilot advised company maintenance personnel of the low oil pressure indications by message through the company dispatch facility in St. John's. Maintenance advised the pilot, via company dispatch, that he should return to St. John's. The relaying of messages between the pilot and maintenance took about six minutes, and the aircraft was, by then, 71 nm from the St. John's Airport and 40 nm from the Gander Airport. The pilot then requested and received a clearance back to St. John's Airport from Gander Area Control Centre (ACC). Four minutes after starting the turn back towards St. John's, an engine vibration developed. The aircraft was 44 nm from the Gander Airport and descending through FL200. The pilot declared an emergency with Gander ACC and was cleared direct to the St. John's Airport. The pilot was initially able to decrease the vibration by reducing the power setting; however, about four minutes later, the vibration became so severe that the pilot had to shut down the engine. The aircraft was approximately 49 nm from the St. John's Airport at an approximate altitude of 13 000 feet when the engine was shut down. The pilot reported to Gander ACC that there was a complete engine failure and asked for vectors to the nearest suitable airport. The nearest suitable airport, St. John's, was beyond the glide range of the aircraft at its present altitude. When the pilot advised Gander ACC of this, the controller provided him with vectors to the Clarenville Airport, the only other airport in the area, which was 20 nm back. Clarenville Airport is located approximately 47 nm southeast of Gander. During the descent toward Clarenville, the pilot requested a report on the local weather in the Clarenville area. Since there is no active weather reporting station in the vicinity of the Clarenville Airport, the Gander ACC requested an estimate of the local weather conditions from the Clarenville detachment of the Royal Canadian Mounted Police (RCMP). The information relayed to the pilot was that the cloud layer was estimated to be above the surrounding hills and the visibility was estimated to be approximately five miles. Approximately 15 minutes after the engine was shut down, the aircraft broke out of cloud over a wooded area at an estimated altitude of 400 to 500 feet above ground level (agl). The front windscreen was obscured with engine oil on the outside and condensation on the inside; consequently, the pilot side-slipped the aircraft to see out the side window. The airport was not visible, and the pilot elected to force-land in a bog. The aircraft was force-landed at approximately 1741, with the landing gear and flaps retracted, 1.5 nm southeast of the Clarenville Airport. 1.2 Injuries to Persons 1.3 Damage to Aircraft 1.4 Other Damage Ground damage was restricted to the impact area of the bog. 1.5 Personnel Information The pilot held an airline transport pilot licence and a valid pilot proficiency check on the PC-12 aircraft. He had a valid medical certificate, signed by a Canadian aviation medical examiner on 28 April 1998. He had also completed all general and specific classroom training required by the Canadian Aviation Regulations (CARs) and the company operations manual to qualify him to act as pilot-in-command on the PC-12 aircraft. 1.6 Aircraft Information 1.6.1 General A review of the aircraft documentation indicates that the aircraft was maintained in accordance with existing regulations and approved procedures. However, in order for an aircraft to be approved for single-engine instrument flight rules (SEIFR) flight, a chip detector system to warn the pilot of excessive ferrous material in the engine lubricating system is required. The design feature of the chip detector installed on this aircraft was such that indications to the cockpit were disabled whenever the landing gear was retracted; therefore, this installation did not meet the requirements of the standard governing the transport of passengers in single-engined aircraft, Commercial Air Service Standard (CASS) 723.22. The aircraft journey log indicated that the aircraft was dispatched on the accident flight with the following deferred defects: Emergency locator transmitter (ELT) removed.--The ELT was removed prior to this flight for maintenance. CAR 605.39 allows for flight without an ELT for up to 90 days; De-ice system inoperative, aircraft restricted.--The outboard de-icing boot on the left wing had been replaced prior to the flight and, because the cure time on the sealant was 48 hours, the system was unserviceable. Low oil quantity light inoperative.--During an unrelated maintenance action prior to the accident flight, the low oil quantity light was observed to be illuminated. The tank level was checked and found to be full. During subsequent troubleshooting of the system, the light extinguished, and maintenance was unable to determine why it had illuminated. The filler cap and indicator assembly were suspected of having an intermittent fault. As an interim measure while awaiting replacement parts, the aircraft was placarded, and a letter was sent to all flight crew advising them that the system was unserviceable and to visually check the oil level before each flight. The pilot had read the letter, and he checked the oil before departing on the accident flight. 1.6.2 Engine Magnetic Particle (Chip) Detector The chip detector system on board the PC-12 is installed at the six o'clock position in the reduction gearbox (RGB). Only the oil lubricating the RGB and a portion of the lubricating oil from the number three and four engine bearings pass over the chip detector before returning to the scavenge oil pump. None of the lubricating oil from the number one and two engine bearings and none of the oil from the accessory gearbox (AGB) pass over a chip detector before returning to the scavenge oil pump. Oil from these areas goes first through the scavenge oil pump, then through the pressure pump and oil filter, before returning to lubricate the engine components. As a result, metal generated in these areas would be filtered out prior to encountering the chip detector in the RGB. 1.6.3 Electrical System The SEIFR requirement for electrical power is for two independent power generating sources, either of which is capable of sustaining essential flight instruments and electrical equipment.(3) The PC-12 meets this requirement with a 28-volt direct current system comprised of a main generator, a secondary generator, and a 24-volt battery. The battery provides power for starting the engine and, in the case of engine failure or failure of both generators, it will power essential electrical systems for 20 minutes if the load is reduced below 60 amps or for 30 minutes if the load is reduced below 50 amps. 1.6.4 Windshield Heat The sole means of defogging and anti-icing the two-piece windshield are twin-zone dual electric heating elements. Windshield heat is controlled by two switches (left-hand and right-hand) and two heat levels (light and heavy), which are to be used as required for defogging and anti-icing. In the event of an engine failure, windshield heat is only available to the pilot's windshield. Data provided by the manufacturer indicate that, in the case of an engine failure, if the pilot's windshield heat is continuously selected on light mode, the duration of battery power would be about 24 minutes; if it is continuously selected to the heavy mode, the duration of battery power would be about 22.5 minutes. The pilot turned off the windshield heat after the engine failed in order to conserve battery power. PC-12 pilots have reported that the windshields in this aircraft will frequently fog over when the windshield heat is not selected. The pilot did not re-select windshield heat prior to nearing the Clarenville Airport, and, when the aircraft broke out of the cloud, the windshield was obscured. In this occurrence, however, because of the combination of fog and oil that was obstructing the pilot's vision, re-selecting windshield heat would likely not have had a positive effect. 1.6.5 Oxygen System The airplane is equipped with an emergency oxygen system for use by the crew and passengers in the event of a loss of pressurization. A fully charged oxygen storage cylinder will supply two crew and nine passengers for ten minutes. 1.6.6 Weight and Balance The weight and centre of gravity were within the prescribed limits. 1.7 Meteorological Information The pilot had received the 1800 UTC hourly weather report for both Gander and St. John's prior to departure. This weather information also included the terminal forecast, winds aloft, significant meteorology reports (SIGMET), and area forecast for Newfoundland and Labrador. After turning back to St. John's, the pilot received the latest St. John's weather. At 1800 UTC, a quasi-stationary low pressure system was 90 nm east of St. John's. There was also a north-south upper trough to the west of St. John's, moving westward. The forecast for the St. John's area indicated a cloud layer at 2 000 to 3 000 feet broken, occasional overcast, with the top of this layer at 8 000 feet. A layer of high, scattered cloud was also forecast with the visibility at greater than 6 statute miles (sm). There would be isolated altocumulus castellanus cloud with the tops at 16 000 feet, giving 2 to 5 sm visibility in light rain showers and mist. Precipitation would become light rain and snow showers after 2400 UTC. The forecast for the Gander area indicated a cloud layer at 1 000 to 2 000 feet overcast with layers up to 18 000 feet. A layer of high, broken cloud was also forecast with the visibility at 3 sm to greater than 6 sm in light rain and mist. There would be scattered embedded altocumulus castellanus and towering cumulus cloud with the tops at 20 000 feet, giving 1 to 3 sm visibility in rain showers and mist. Precipitation would become occasional light rain and snow after 2400 UTC. The icing forecast for the area indicated moderate mixed icing in altocumulus castellanus / towering cumulus; otherwise light to moderate rime icing above the freezing level. The freezing level was to be at or near the surface. The hourly weather report for St. John's Airport at 1800 UTC was: Surface winds 340 degrees true at 15 knots, visibility 15 sm, cloud layers 700 feet broken / 1 000 feet overcast, temperature 3 degrees Celsius, dewpoint 2 degrees, altimeter 29.46. Remarks: cloud type and coverage was stratus fractus six-eighths and stratocumulus two-eighths. The hourly weather report in effect at St. John's Airport at the time of the occurrence was the 1900 UTC observation, as follows: Surface winds 340 degrees true at 14 knots, visibility 15 sm, cloud layer 600 feet overcast, temperature 3 degrees Celsius, dewpoint 2 degrees, altimeter 29.48. Remarks: cloud type and coverage was stratus fractus eight-eighths. The terminal forecast for St. John's Airport from 1700 to 2000 UTC was: Surface winds 360 degrees true at 20 knots, visibility 3 sm in light drizzle and mist, cloud layers 600 feet overcast, temporarily more than 6 sm visibility, no significant weather, cloud layer 800 feet overcast. The hourly weather report for Gander Airport at 1800 UTC was: Surface winds 340 degrees true at 19 knots, visibility 3 sm in light rain and mist, cloud layers 200 feet broken / 600 feet overcast, temperature 2 degrees Celsius, dewpoint 1 degree, altimeter 29.63, recent moderate rain. Remarks: cloud type and coverage was stratus fractus seven-eighths and stratocumulus one-eighth. A special weather report issued at 1941 UTC was in effect at Gander Airport at the time of the occurrence, as follows: Surface winds 350 degrees true at 15 knots, visibility 2 sm in light rain and mist, cloud layer 300 feet overcast, temperature 2 degrees, dewpoint 2 degrees, altimeter 29.63. Remarks: cloud type and coverage was fog two-eighths and stratus fractus six-eighths. The terminal forecast for Gander Airport from 1600 to 2200 UTC was: Surface winds 360 degrees true at 20 knots, visibility 3 sm in light rain and mist, cloud layers 300 feet broken / 600 feet overcast. There was no SIGMET or pilot report (PIREP) in effect for the area at the time of the occurrence. 1.8 Aids to Navigation The pilot was assisted in his navigation by radar vectors and the use of the onboard global positioning system (GPS). There are no ground-based aids to navigation at the Clarenville Airport. 1.9 Communications Communications were maintained between the aircraft and Gander ACC until just prior to impact with the ground. 1.10 Aerodrome Information Clarenville Airport is certified and operated by the Government of Newfoundland and Labrador. The single runway (08/26) is 3 933 feet long. The airport is suitable for PC-12 aircraft visual flight rules (VFR) operations. 1.11 Flight Recorders The aircraft was not equipped with a flight data recorder or a cockpit voice recorder, nor was either required by regulation. 1.12 Wreckage and Impact Information 1.12.1 Site Examination The first impact was with the tops of four small spruce trees at the edge of the bog. The angle at which the tops of the trees were broken is consistent with the aircraft being in a 15-degree, left-bank attitude when it struck the trees. The first ground impact was when the left wing tip contacted the bog approximately 63 feet beyond the broken trees and dug a 58-foot-long gouge in the bog on a heading of 270 degrees. The outboard six feet of the left wing was located at the end of the long gouge. The next point of contact with the ground was a large oval-shaped crater 20 feet beyond the end of the gouge. The shape of this crater is consistent with the aircraft fuselage striking the ground at this point. The engine and engine mount separated from the aircraft in the area of the large crater. After the initial fuselage ground contact, the aircraft skipped forward approximately 75 feet while rotating counterclockwise through approximately 180 degrees, before touching the ground again with the trailing edges of first the right wing, then the left wing. This is consistent with impact marks on the trailing edge of the right wing and is probably the initiation point for the remainder of the left wing separating from the aircraft. The aircraft then skipped another 75 feet, still rotating counterclockwise, before coming to rest on a heading of 225 degrees, with the engine underneath the right wing. The left wing, which separated from the aircraft at the root, was wedged in the ground, underneath the tail of the aircraft. Heavy oil streaks were observed along both sides of the fuselage, as well as lighter traces of oil on top of the fuselage. There was oil on the windscreens during flight, which affected the pilot's ability to see outside, but the windscreens broke out of the aircraft during impact, and it was not possible to determine how much oil had been on them. 1.12.2 Engine History The engine, Pratt Whitney (PW) PT6A-67B, serial number PR0003, was installed as original equipment on the aircraft. On 19 September 1997, at 1 825 total engine hours, the engine was removed from service and sent to PW for examination and repair due to regular findings of carbon in the oil filter and discolouration of the oil. After repair, the engine was reinstalled in the aircraft on 09 March 1998. On 04 May 1998, at 2 387 total hours, the compressor was borescoped in response to an unconfirmed change in the gas producer run-down time; no defects were found. The starter-generator garlock seal and oil pressurizing valve were replaced at this time due to oil consumption reported at two quarts in 12 hours of engine operation. On 05 May 1998, at 2 400 total hours, the fuel control unit and high-pressure fuel pump were replaced due to slow starting. On 09 May 1998, the starter-generator garlock seal was again replaced due to continued high oil consumption; there were no further reports of high oil consumption. Analysis of oil samples taken on 12 May 1998 did not indicate engine deterioration. A review of the journey log sheets back to when the occurrence engine was re-installed in the aircraft showed a consistent variance for recorded oil pressure entries from one pilot to the next. The range was from 110 to 125; however, the recording for each individual pilot was always consistent. The pattern in which these oil pressure variations appear suggests that they were due to the manner in which the oil pressure was being read and recorded by each pilot, rather than being actual variations in oil pressure. 1.12.3 Engine Teardown and Examination The engine was shipped to the PW facility in Longueuil, Quebec, where a teardown examination was conducted under the supervision of a TSB investigator. It was determined that the engine failed as a result of an interruption of oil flow to the first-stage planet gear assembly in the RGB. There was no service history of a similar failure and, despite extensive examination and testing on the engine and related systems and components, no cause for the interruption in oil flow to the first-stage planet gear assembly could be found. Other noteworthy findings of the teardown examination were that no other areas in the engine had signs of oil supply starvation, including the second-stage planet bearings, and that the power turbine had separated from the reduction gear drive (as a result of the oil flow interruption), shedding its blades from the resultant overspeed condition. (The blades were contained within the engine casing.) 1.13 Medical Information There were no indications of pre-existing medical conditions that would have adversely affected the pilot's performance. 1.14 Fire There were no signs of pre- or post-impact fire. 1.15 Survival Aspects The passenger cabin remained intact, and the main cabin door, the cargo door, and the over-wing exit were all operable. The forward passenger seat on the right-hand side became detached from the seat rails during the accident sequence. Neither the seat rails nor the seat-to-rail attachment points exhibited any signs of damage, and the locking mechanism functioned as designed; this suggests that the seat may not have been locked in place. The pilot and company observer were trapped in their seats by the rearward displacement of the instrument panel and the upward displacement of the cockpit floor during impact. One of the passengers took charge of getting the other passengers out and away from the aircraft and of providing first aid care to the pilot and the observer. He then collected some fuel that was spilling from a ruptured fuel line and started a fire to keep the passengers warm. Upon being notified of the impending crash, the RCMP activated the local ground search-and-rescue team and chartered a helicopter from a local operator. An air search was conducted in the general area of the accident before a signal flare was seen. The accident site was located at 1845, approximately one hour after the accident had occurred. A search-and-rescue Labrador helicopter arrived at the scene at 1900, and all the occupants were evacuated from the scene by 2045. This was the aircraft's first flight since the ELT had been removed for maintenance. The general location of the aircraft was known, the crash site was in a large open bog, one of the passengers was able to fire a flare, and the ceiling and visibility allowed a visual air search. Therefore, the absence of an ELT did not have a detrimental effect on locating the aircraft. However, the remoteness of the flight's planned route supports the importance of an ELT. 1.16 Tests and Research No tests or research were conducted. 1.17 Organizational and Management Information At the time of the occurrence, the company operated two aircraft, a Beech 1900 and the Pilatus PC-12. The Beech 1900 was used primarily for cargo operations and occasionally for passenger-carrying charter flights. The primary use of the PC-12 was cargo operations; it was also used for scheduled passenger flights which consisted of a once-daily Goose Bay-St. John's-Goose Bay flight, six days a week. The PC-12 aircraft was changed from passenger configuration to cargo configuration and vice versa during the station stops in Goose Bay, which were approximately 30 minutes in duration. The company observer usually installed the seats. 1.18 Additional Information 1.18.1 SEIFR Flight Prior to adopting a policy on the carrying of passengers on SEIFR flights, Transport Canada (TC) conducted a study on SEIFR and published a position paper in December 1993. The paper concluded that the proven reliability of modern turbine engines installed in modern, factory-built, turbine-powered airframes with modern avionics made SEIFR feasible and that the risks inherent in such a policy were manageable. The results of the study were submitted to TC's System Safety Directorate for an independent operational safety review. The Directorate, after studying all aspects of the policy and discussing it with other technical experts, concluded that the risks were indeed manageable. Finally, the proposed policy was subjected to consultation with interested segments of the Canadian aviation industry and, after no dissenting opinions were received, CAR 703.22 and CASS 723.22, the regulation and standard governing the transport of passengers in single-engined aircraft, came into effect. Included in the proposed SEIFR policy was a condition in the required equipment list (REL) for a maintenance system capable of automatically monitoring and recording those parameters critical to engine performance and condition. However, this condition did not form part of the REL outlined in CASS 723.22. The proposed SEIFR regulations for Australia and the Joint Aviation Requirements for Europe do list an automatic trend monitoring system as a condition in the proposed REL. Although the United States Federal Aviation Regulations (FARs) governing SEIFR operations do not call for an automatic trend monitoring system, they do require that the operator's maintenance inspection program include either the manufacturer's recommended trend monitoring program or a Federal Aviation Administration (FAA)-approved trend monitoring program. Canadian regulations do not require a SEIFR operator to incorporate engine trend monitoring in his or her maintenance program. Standard Operating Procedures (SOPs) are a regulatory requirement for commercial operations where the aircraft must be operated by two or more pilots; however, SOPs are not required for commercial single-pilot operations. The operator in this occurrence did not have SOPs pertaining to the operation of the Pilatus aircraft. 1.18.2 Training Requirements for SEIFR To act as pilot-in-command on aircraft approved for SEIFR flight, pilots are required to have training in an approved synthetic training device (simulator). There is now an approved PC-12 simulator available for training; however, when the PC-12 was first certified for SEIFR flight, there was not. Consequently, TC issued a waiver allowing SEIFR operations in this aircraft, provided the pilots had training on the Cessna 208 simulator. The pilot had completed the required simulator training in the Cessna 208 simulator. 1.18.3 Pilot Decision-Making Training There is no regulatory requirement for SEIFR operations pilots to have received pilot decision-making (PDM) training. However, this appears inconsistent in that the standard for reduced VFR limits, CASS 723.28 VFR Flight Minima--Uncontrolled Airspace, requires pilots to have PDM training. The occurrence pilot had not attended a course in PDM. TC-recognized PDM courses must include the following topics: The Decision Making Process including modules on psychological factors, levels of performance, and error trap phenomena (unsafe actions taken as a result of wrongful assumptions, unsafe conditions or practices). Human Error Countermeasures highlighted by relevant case studies of past accidents. 1.18.4 Emergency Procedures Section 3.6, Engine Emergencies, of the pilot operating handbook (POH) describes the procedures to be followed for low oil pressure indications: Ng check above 72% Torque Reduce to below 24 PSI Aircraft Land as soon as practical. Aircraft Land as soon as possible using minimum torque. Aircraft Land as soon as possible using minimum torque. If possible always retain glide capability to the selected landing area in case of total engine failure. The POH does not define the terms Land as soon as practical and Land as soon as possible; however, these terms are generally accepted to mean the following: Land as soon as practical--Landing airport and duration of flight are at the discretion of the pilot. Extended flight beyond the nearest suitable airport is not recommended. Land as soon as possible--Land without delay at nearest airport where a safe approach and landing is reasonably assured. 1.18.5 Previous Low Oil Pressure Indications A few months prior to this occurrence, during the time when a loaner engine had been installed in the aircraft, the pilot reported that he had experienced, on a couple of occasions, the oil pressure dropping into the lower part of the green band during climb and then returning to normal after levelling off. The pilot reported that he thought that the same thing was recurring on the accident flight and that the unserviceable low oil quantity annunciating system was also related to the low oil pressure indications he was experiencing. 1.18.6 Aircraft Glide Performance Calculations Calculations determined that if the pilot, at the time engine vibrations occurred, had immediately turned back to Gander and maintained 22 000 feet, he could have reached the airport. It was also determined that if he had remained at 22 000 feet until the engine was eventually shut down, he could have reached St. John's. The PC-12 maximum operating altitude is 30 000 feet and, for a single-pilot operation with passengers, 25 000 feet. For the purposes of discussing battery and oxygen system requirements, calculations determined that at the optimum glide speed, the aircraft would descend from 30 000 feet to sea level in 32.5 minutes, and the time from 25 000 feet to 13 000 feet would be 11.5 minutes. 1.18.7 Regulatory Requirement for De-icing Equipment CAR 605.30 requires that the pilot-in-command determine that the aircraft is adequately equipped to operate in icing conditions if icing conditions are reported or forecast. Icing conditions were forecast for the route of flight.